Duplicating



1965 R. w. GUNDLACH ETAL 3,170,395

DUPLICATING Filed Oct. 7, 1963 3 Sheets-Sheet 1 I2\ FIG. 1

FIG. 2

'25 POWER SOURCE FIG. 3

A T TORNE Y DUPLICATING 3 Sheets-Sheet 2 Filed Oct. 7, 1963 SIDE '2 SIDE l A t tu :1 H mg gm? :rrm

A 25 a wig" w FL M m: it 5. @1552;

FIG. 7

FIG. 8

FIG. 10

FIG. 9

FIG. 12 mvsmons ROBERT W. GUNDLACH VSEVOLOD S lgAJLOV g ATTORNEY FIG. 11

1965 R. w. GUNDLACH ETAL 3,170,395

DUPLICATING Filed Oct. 7, 1965 3 Sheets-Sheet 3 FIG. 14

INVENTORS ROBERT W. GUNDLACH VSEVOLOD S. MZAJLOV BY% W 465% A T TORNE Y and expense of producing multiple duplicates of original copy by present methods. For example, it has been the common practice in clerical work to produce the desired number of copies using carbon paper. This not only increases the difficulty in handling but also makes it quite difficult to correct errors since each sheet must be corrected individually. 'Many duplicating machines are available for duplicating printed and other material by processes such as xerography, photo-copying, thermo and diazo processes. However, each of these processes require apparatus of some substantial complexity and/or expense. Less expensive duplicating processes such as spirit-duplicating processes and stencil-duplicating processes fall short of the desired characteristics on two points. Operators find that both of these are very messy so that ink or dye stains usually end up on the hands and clothes, and further that the copies made are very poor in image sharpness. This loss of sharpness in the case of spirit duplicating is due to slight bleeding of the dye due to the solvent action on the copy paper. In the case of stencil duplicating, bleeding occurs in the stencil due to the necessary characteristic of the stencil material required to permit passage of ink in the character areas.

Also, it is a common characteristic of the less expensive duplicating processes that they require some form of master or stencil which must be made up as by typing, handwriting, or in a way similar to that for making an original and is itself not suitable for use as an original document. The making of such stencils commonly adds all the disadvantageous effects that are found when using carbon paper in making duplicate copies. Now in accordance with the present invention, it has been found that by using color reagents and evaporation transfer tech niques it is possible to greatly simplify low volume duplicating processes. One typewritten copy can be made using a color reagent and the color reagent can then be transferred to a duplicating master quickly, cheaply, and easily without any loss of quality in the typewritten original. Thus, the original continues available for use as an original copy and originals which are received are readily made into multiple copies without impairing the original which in many instances must be preserved. In this manner the use of carbon paper copies is avoided, the use of expensive duplicating equipment is avoided,

and high resolution copies can be produced rapidly, cheaply, and neatly. Thus, it is an object of the present invention to define a novel copying process.

It is a further object of the invention to define a method of duplicating two sides of a single page original.

It is an additional object of the invention to define apparatus for duplicating a two-sided original to form a two-sided duplicate copy.

Further objects and features of the inventionwill become apparent while reading the following description in connection with the drawings wherein:

FIG. 1 is a cross-sectional view of one embodiment of a typewriter ribbon carrying a color reagent;

United States Patent "ice 3,17,395 Patented Feb. 23, 1%65 FIG. 2 is a face view of a second embodiment of types writer tape carrying a color reagent;

FIG. 3 is a diagrammatic illustration of simplified apparatus for carrying out one step of the inventive process;

FIG. 4 is a'diagrammatic illustration of the simplified apparatus shown in FIG. 3 particularly illustrating a sec ond step in the process;

FIGS. 5 and 6 are diagrammatic illustrations of rotary apparatus for carrying out the process steps shown in FIGS. 3 and 4, respectively.

FIG. 7 illustrates one side of an original prepared in accordance with the invention;

FIG.' 8 illustrates a second side of the original illustrated in FIG. 1; 7

FIGS. 9-l2 are process flow steps in accordance with the invention; v

FIG. 13 is a first embodiment of apparatus in accordance with the invention; and,

FIG. 14 is a second embodiment of apparatus in accordance with the invention.

For simplicity of illustration, the invention will be de scribed using a typewriter to produce the original. As will be set forth below, however, this is only by way of example and the invention comprehends various other modes of producing the original.

In producing a'typewritten original in accordance with the instant invention, the usual typewriter ribbon for a typewriter is replaced with a similar ribbon which has been inked with a conventional typewriter ink and also with a color reagent. This color reagent, which is herein termed Chemical A, may be one of a number of chemicals for which a reaction partner exists so that when the two are combined, an intensely colored substance is formed. The reaction partner is herein termed Chemi cal B. Following is a partial listing of suitable materials for Chemical A With corresponding reaction partners, Chemical B:

Chemical A Chemical B (1) Iron salts. (2) Vanadium salts.

Potassium dichromatc. (3) Copper salts.

Nickel salts. Cobalt salts.

(1) Pyrocateehol (2) Aniline (3) Dithiooxamide N-dimethyl-dithiooxarnide. N .I{-bis(2-hydroethyl)dithiooxa- (4) Silver salts.

(5) Organic diazonium salts and coupler.

As will be further described below, material typed using the ribbon containing Chemical A may be used to form a mirror-image master from which, in turn, multiple direct-reading copies may be produced on paper treated with the corresponding Chemical B.v

FIGS. 1 and 2 show various embodiments of typewriter ribbon in accordance with the invention. In FIG. 1, the typewriter ribbon comprises support tape 11 carrying composition 12 of ink and an appropriate Chemical A. Support tape 11 can be any material suitable for use as a typewriter ribbon such as cloth fabric, metal foil, paper, or plastic. Because non-uniformities are emphasized in a duplicating process, the support tape is preferably of a material that facilitates uniform typing. As is well known in the typewriter industry, greater uniformity is commonly achieved by using a non-reusable ribbon. Such ribbons are conventionally referred to as carbon ribbons and use a thin plastic support tape. In a preferred embodiment, typewriter ribbon for use in accordance with the present invention comprises a polyethylene film coated with typewriter ink and Chemical A in which Chemical A is about 50% by weight of the ink and Chemical A mixture. Spray coating, roll coating, dip coating, evaporation coating, or other conventional coating means may be used. Alternatively a cloth ribbon is saturated with an ink and Chemical A, of the same nature as for the plastic ribbon, by running the ribbon through a bath of the solution or by some similar process. For example, a silk typewriter ribbon dipped in a mixture of 20 grams rubeanic acid to 100 grams of black typewriter ink.

FIG. 2 shows an embodiment of a typewriter ribbon 14 in accordance with the invention in which one half of the ribbon 15 is coated or permeated with the ink and color reagent solution as in FIG. 1 and the other half of the ribbon 16 is coated with a chalk-like material for correcting errors. The correcting materials are picked for their ability to conceal a type letter when the same letter is typed over with the error-correcting half of the ribbon, and further for their ability to form a vapor block so that no vapor can issue from the erroneously typed letter. For example, titanium dioxide or zinc oxide in a wax binder or the like have been found suitable for coating the correction half of the ribbon. Using a ribbon of the type illustrated in FIG. 2 and typing only a single copy increases ease of typing tremendously since the typist does not have to worry about material on carbon copies and, in correcting an error, does not have to use anything outside of the typewriter, itself, such as erasers or other materials available for correcting typewritten material. The typist merely backspaces, pushes the ribbon-position lever and retypes the letter in order to obliterate it. Thus, the typists hands are not required to leave the keyboard of the machine in correcting errors.

In accordance with the invention, a single sheet of original typed copy is made using a ribbon in the typewriter corresponding to one of the embodiments illustrated in FIGS. 1 and 2. It is desirable that the typing be highly uniform in order to obtain good copies. Since the average typist does not have good uniformity of touch, an electric typewriter has been found preferable.

FIG. 3 shows a simple manually operated embodiment of apparatus to produce multiple copies of the typed original. This apparatus comprises heat conductive pad 18 such as will maintain a uniform low ambient temperature on its surface when a heated roller is rolled across a sheet of material resting on such surface. Thus the heat conductive pad may be a metal such as aluminum having enough mass to absorb a considerable amount of heat without changing its over-all temperature by a significant amount. This pad should have a surface area adequate to support the largest size of copy sheet that may be desired. A rectangular size of about 10 x 15 inches is adequate for most purposes. The pad should preferably'be not less than one quarter inch thick, but this is not limiting since the heat absorption and dissipation characteristics are controlling.

In accordance with the inventive process, master sheet 19 is positioned in contact with the surface of the heat conductive pad. This master sheet may be made of substantially any material that has a smooth finished surface such as a majority of plastic materials, metal foils, glass or paper. By way of example a 1 mil thick sheet of cellulose acetate has been used. Nonporous materials have generally yielded the best results but whether this is due to thermal characteristics, absorption characteristics, or some other characteristics is not fully understood at this time. Thickness of the master sheet is not critical and success has been obtained with sheets of 1 mil and of 15 mils thickness. The determining criteria relevant to this last characteristic are the amount of heat available and the permissible time for vaporizing volatile material from the surface of the master sheet. An excessive thickness will either act as a heat insulator or will dissipate the heat too rapidly for eflicient operation. It is preferably less than about 10 mils thick so that it will not absorb or hold an excessive amount of heat. A 3/32 inch thickness of window glass has been found suitable by way of example.

Typed original 20 is next placed face down against the smooth surface of the master sheet and heated roller 22 or other heat applicator such as a heated plate or heat lamp is used to apply heat against the back of typed original 20. Heat applicator 22, as illustrated, is a metal roller containing thermal element 23 which is connected through handle 24 of the roller to power source 25. In rolling the roller against the back of the typed original or in applying heat in one of the other ways suggested, the intensity of the heat and the length of time must be such as to cause a portion of Chemical A in the characters of the typed original to sublime or otherwise change to a vapor. Suitable heat may be applied by operating the roller at a temperature of about 200 to 400 F. and by rolling the heated roller across the back surface of original 20 at a speed of about /2 to 4 inches per second. With the roller at 240 a speed of about 1 inch per second has been used. These ranges have been found suitable using rubeanic acid as Chemical A. While still higher temperatures produce good results at faster speeds, such temperatures increase the likelihood of heat damage to the materials or equipment. Safeguards against such damage can be built in, but would increase expense. In the apparatus of FIG. 4, heat conductive pad 18 maintains master sheet 19 at a temperature relatively lower than that attained by typed original 20 when the heat is applied to it. Thus, a portion of the color reagent Chemical A is transferred by vaporization and condensation from the typed original to the master sheet. Since the material thus transferred is transferred between surfaces that are in virtual contact, there is no significant loss of resolution. Since the amount of liquid transferred is very minute, bleeding effects are practically nonexistent.

After the color reagent, Chemical A, has been thermographically transferred to master sheet 19 as described above in connection with FIG. 3, the master sheet is removed from pad 18. Then as illustrated in FIG. 4, copy sheet 27 treated with Chemical B is positioned on pad 18 with its treated surface facing away from the pad. Copy sheet 27 may comprise any ordinary paper which has been chemically treated in accordance with the invention. Preferably, the paper is smooth surfaced to permit a more uniform contact in the duplicating process. If the color reagent, Chemical A, is dithiooxamide, otherwise known as rubeanic acid, the copy paper is appropriately treated with a coating solution of, for example, nickel salts dissolved in water, alcohol or similar solvent to a solution of 5% to 25% by weight volume. For improved density, it has been advantageous to add an amine in which one or more hydrogen atoms attached to nitrogen have been replaced by one or more alkanol groups. A suitable amount of this additive has been found to be 0.5 to 4.0 moles per mole of nickel. This additive is also advantageously used with the other metallic salts listed under Chemical B. One coating solution used is a 25% solution of NiSO 6H containing two moles of 2-(2-aminoethyl) aminoethanol per mole of nickel. A solution of 25% weight by volume of copper sulfate in water has also produced effective results. The solution may then be coated on the paper by spraying, dipping, flowing, rolling, wiping or similar process. Some moisture content in the copy paper has been found to increase density further. Thus casein coated papers or paper treated with a humectant such as a sorbitol or glycerine have been found advantageous.

master sheet, a portion of the color reagent, Chemical A, in character configuration on the master sheet is transferred by evaporation to the surface .of the copy sheet. Where Chemical A contacts the copy sheet, it reacts with its reaction partner, Chemical B, on the copy sheet to produce a visible image.

Since transfers by the process described above are always by face-to-face contact in the embodiments described above and since the colored product is insoluble preventing bleeding, a very high resolution is obtainable in the copy.

In a further embodiment of the invention, it is possible to eliminate master sheet 19 described in FIGS. 3 and 4, but with a slight loss in resolution. In this further embodiment, treated copy sheet 27 is placed with its treated surface adjacent to the surface of pad 1%. Then typed original 20 carrying Chemical A in its typed characters, is positionedwith its typed surface adjacent to the untreated surface of copy sheet 27. When heat is applied as by roller 22 or other heat applicating means, Chemical A vaporizes and condenses on copy sheet 27. If copy sheet 27 is made of a very porous paper or paperlike material, some of the vapor will pass through the pores reaching the treated surface of the copy paper. Otherwise, Chemical A should be chosen as a material that does not sublime but passes through a liquid phase. When this material condenses as a liquid on the untreated surface of the copy sheet, it is absorbed by the copy sheet and passes through in order to react with the reaction partner, Chemical B, on the opposite surface of the copy paper. As is apparent, in order to maintain an acceptable level of resolution, the copy paper in accordance with this embodiment should preferably be quite thin, in the nature of 21. mil or less. However, thicker copy papers may be used with the attendant disadvantage of slightly lower resolution. A second method for going directly from original to copy requires the use of substantially transparent copy sheets. The transparent copy sheet carrying Chemical B is positioned with its coated surface facing the typed surface of the original. The two are heated causing vaporization and chemical reaction on the contacting surface of the copy sheet. The image is then directly readable through the reverse side of the copy sheet.

FIGS. 5 and 6 show an embodiment of simply rotary apparatus for performing the process illustrated in connection with FIGS. 3 and 4. In this embodiment, cylinder 31 and cylinder 32 perform the functions of pad 18 and roller 22, respectively, of FIG. 3. It is considered preferable that one of the cylinders have a slightly yieldable coating and high friction qualities. For example, covering one cylinder with a surface layer of silicone rubber has been found advantageous. Thus, cylinder 32 is a heated cylinder. In this embodiment, the thermal characteristics of cylinder 31 are not particularly critical. However, it has been found that cylinder 31 because of its close proximity in operation to cylinder 32 is inclined to draw heat from cylinder 32 reducing its temperature and causing non-uniform heat distribution. Thus it is preferable to heat cylinder 31 as well as cylinder 32 as illustrated by thermal elements 23, or to cover 7 cylinder 31 with a heat insulating layer so as to reduce heat dissipation. Good results have also been obtained by heating only cylinder 32, but maintaining the two cylinders in continuous rotating contact for an extended period prior to use so as to reach a point of temperature stability. With the temperature on heated cylinder 32 stabilized in the range between 200 and 400 F., master sheet 19 and typed original 2% are run in between cylinders 31 and 32 and advanced by rotation of the cylinders, 7 Motor 33 is illustrated as driving cylinder 31 through drive means 34. However, it should be understood that the same operation can be performed by a manual crank. As the two sheets run between the two cylinders, heat from heated cylinder 32 penetrates to the characters in the typed original and causes color-reagent Chemical A to vaporize into the minute space between the two sheets. It is pointed out that this minute space is the natural result of positioning two smooth sheets in contact. A mere positioning of two sheets in contact in this manner even when they are run between pressurerollers will not eliminate all space between the contact ing surfaces. Minor variations always present in such surfaces prevent complete elimination of such space. As the two sheets pass between the two cylinders, some Chemical A is transferred to the master sheet. The image on the master sheet is commonly a weakly visible image.

While not necessarily limiting as to how the transfer of Chemical A actually takes place, it is theorized that it vaporizes due to the heat'between the two sheets and then as the two sheet-s issue from between the cylinders, they are cooled by the ambient temperature of the air so that condensation or sublimation of Chemical A occurs in part on both surfaces. It has been found that transfers of Chemical A to the master sheet have consistently attained levels of 75% or more transfer. While the reason for this is not completely understood, it is possibly due to the use of master materials which are relatively more heat conductive than the paper used for the original. This would allow the master to cool faster and thus condense the evaporate chemical at a higher rate than the original. It should be noted that in this embodiment there is no requirement asto whether the master sheet or the typed original is in direct contact with the heated cylinder. It is only necessary that enough heat be applied to one or the other so that heat penetrates the sandwich and volatilizes some of the color reagent.

Next, as illustrated in FIG. 6, a treated copy Sheet is positioned with its treated surface in contact with the surface of the master sheet now carrying transferred Chemical A in the configuration of the original. The two sheets are advanced as a sandwich between cylinders 31 and 32 in a second vapor-thermographic transfer process similar to that illustrated in FIG. 4. Again the heat may be applied to either surface of the sandwich so long as it is adequate to cause vaporization of some of the Chemical A present on the master sheet. As the two sheets pass between the cylinders, Chemical A is transferred to the copy sheet.

A particular novel feature of the present invention is its unusually facile adaptation to two sided copying. FIG- URES 7 through 14 relate to embodiments of the present invention for reproducing copies on two sides.

FIG. 7 illustrates thefront side of a document typed with a typewriter ribbon containing Chemical A such as rubeanic acid.

FIG. 8 shows the backside of the same document also typed with a typewriter ribbon containing Chemical A. A good quality bond paper is satisfactory for preparing the original. This paper is not particularly critical. However, tissues, light-weight paper or relatively porous paper should not be used because of a tendency to produce cross-talk between the two sides so that some of the image from one side of the sheet may appear as ghosts on the wrong side of the copy paper.

FIG. 9 illustrates the original document 41 of FIGS. 7 and 8 positioned inside a sleeve of master material depicted in this figure as a foldedsheet having a first side 42 against which the back of original document 41 is positioned, and a second side 43 which is then folded across the front side of the original document.

While illustrated in FIG. 9 as a folded sheet, the sleeve of master material may also be a complete sleeve open only at the ends to permit insertion and removal of the original and copy sheets. The master material may be made of substantially any material that has a smooth finished surface such as a majority of plastic materials, metal foils, glass or paper. By way of example, a sheet of cellulose acetate has been used. Aluminum foil has also proven satisfactory. The thickness of the master material is not critical and success has been obtained with sheets of 1 mil. and of mils. thickness.

FIG. 10 illustrates the first transfer step in which volatile chemical reagents are transferred from the original document to form a mirror reverse image on the inside surfaces 42 and 43 of the master sleeve. This transfer is performed by running the sandwich comprised of the original document disposed between the two sides of the master sleeve in between two hot surfaces such as two heated rollers 45 and 46 containing heating elements 4'7 such-as electrical resistance heating elements. The heat of rollers 45 and 46 causes a portion of the volatile color reagent to evaporate or sublime between the surfaces of the original document and the master sleeve. On cooling, a portion of the chemical reagent is formed on the inside surfaces of the master sleeve in the configuration of the markings on the original. After passage between the heated rollers, the original document is withdrawn from the sleeve. There is no danger of smearing the image in this withdrawal since normal ambient conditions immediately cool the master material back to a temperature at which the chemical color reagent again solidifies.

A sheet of copy paper treated with an appropriate Chemical B, a color reaction partner for the particular Chemical A used in marking the original, is positioned inside the master sleeve similarily to the way in which the original document was positioned. There is nothing particularly critical about the base material for the copy paper, however, the copy paper should be sized on both sides as by casein coating. It has been found that an unsized surface tends to give a relatively diffuse image of poor resolution. The sized copy paper is treated with a solution of Chemical B either as a separate step or by incorporation in the sizing material. It should be noted that the sizing and color reagent material is applied nearly as economically to both sides of the sheet at once as to one side only, so that the copy sheet treated on both sides has very little cost differential as compared to copy sheets treated on one side only.

The sleeve containing the treated copy paper is then passed between heated rollers 45 and 46 as illustrated in FIG. 12. The heated rollers 45 and 46 which are appropriately the same for use in the process steps of both FIG. 10 and FIG. 12 are suitably run at temperatures of about 200 to 460 F. and at a speed of about /2 to 4 inches per second. Higher temperatures enable higher speeds but at the same time increase the likelihood of thermal damage or fire, in the case of improper operation.

After the sleeve containing the copy paper has been run through the heated rollers, the copy paper is removed from the sleeve and will carry intensely colored reproductions on both the front and back side of the material on the corresponding sides of the original. Further sheets of copy paper can be inserted inside the sleeve one at a time and run between the heated rollers to form a plurality of two sided copies.

In the final imaging step, as illustrated in FIG. 12, the heat causes some of the volatile chemical reagent A to evaporate or sublime with some of it transferring to the copy sheet where it contacts and reacts with its color partner Chemical B forming an intensely colored reaction product in image configuration on the copy paper.

While the above description describes the use of two rotating heated cylinders for applying heat in the imaging process, these cylinders may be replaced by two heated plates in the form of a press. The sandwich comprising the master sleeve containing either an original document or the copy paper is placed in the press and the heated plates are brought together to apply heat. After a suitand '72.,

able interval of time the plates are separated and the sandwich is removed from the press.

An embodiment of an automatic machine for producing two-sided copies from a two-sided original is illustrated in FIG. 13. In the embodiment of FIG. 13 two cylinders 5t and 51 are driven in rotational contact with each other by motor 52 operating through drive belts 53 and 55. Cylinders 50 and 51 carry layers 56 and 57 covering at least a portion of the surfaces of the cylinders. The exposed surfaces of layers 56 and 57 should be hard and glossy for easy cleaning. Polished metal, polytetrafiuorethylene or glass are appropriate surfaces for this use. This surface layer for cylinders Etl and 51 may be the polished surface of the cylinder material itself. Positioned adjacent to each cylinder in the direction of rotation after the point at which the two cylinders ran in contact is a cleaning station. Cleaning station 58 adjacent to cylinder comprises container 6%) carrying solution 61 which is a solvent for Chemical A. Suitable solvents are alcohol, benzeneacetone or the like. A rotating sponge or fine brush 62 rotates through the solvent solution and against the cylinder for cleaning the residual Chemical A off surface layer 56 upon completion of a duplicating cycle. Adjacent to the rotating sponge or brush 62 is a squeegee blade 63 which serves to squeegee solvent solution remaining on cylinder 50 off the cylinder and back into container 6t) leaving a clean surface layer 56 for reuse. Cylinder 51 contains an infrared heat source 65 for heating infrared absorbent material passing between the cylinders to an appropriate temperature between about 200 and 400 F. Cylinder 51 must be transparent to infrared to permit heating. Positioned adjacent to cylinder 51 is a second cleaning station 66 similar to station 55. This apparatus also includes a feed tray 67 and a receiving tray 68. A feed dog 76) is positioned for operation with respect to feed tray 67 and is driven in synchronism with the rotation of cylinders 50 and 51 so as to feed copy sheets between the cylinders in proper alignment.

In operation, a stack of copy sheets treated with a color reaction partner on both sides is placed in feed tray 67 with an original marked with a volatile color reagent on top of the stack. Motor 52 is actuated and the original document is fed by feed dog 70 in between cylinders 5t? and 51. Heat applied from the infrared source then drives some of the volatile color reagent from the original onto the surface layers 56 and 57 of the respective cylinders. The original then passes into the receiving tray and the treated copy sheets are fed between the two cylinders where heat from heat source 65 drives some of the color reagent onto the copy sheets in the marking configuration of the original to form reproductions on the copy sheets. After the copies are made, the cleaning stations 58 and 66 are brought into contact with the cylinders so that the remaining volatile chemical reagent is wiped off the cylinders.

The apparatus described in FIG. 13 uses cylinders having master duplicating surfaces. These surfaces must be cleaned each time a new original is used. A machine of somewhat simpler and less expensive design can be made by using throwaway masters which need no cleaning. Thus, FIG. 14 illustrates an embodiment of duplicating apparatus using removable belt type duplicating masters which may be removed and replaced for each cycle of operation. A cycle of operation is used herein to encompass the process of transferring the image forming material from the original to the master and then running off the total number of copies desired from the master. The apparatus in FIG. 14 has two heated drive rolls 71 eated by internal heating elements 73 and '75. These drive rolls are mounted for rotation in contact with each other. Such contact is preferably a spring loaded contact to allow for variations in thickness of material passed in between the rollers. The rolls 71 and 72 are driven by motor 76. Support rolls 7'7 and 78 are positioned a distance from the respective rolls 71 and 72 so as to support master sheets in the form of belts as will be described below. A supply tray 80 is positioned on one side of the two drive rollers together with a feed dog 81 for feeding papers from the supply tray between the two driverollers. On the other side of the drive rollers from the supply tray is a receiving tray 82 for receiving the papers fed between the rollers. Feed dog 81 is driven in synchronism with the drive rolls 71 and 72 so as to maintain the proper position of the material being copied on the copy paper. In operation, drive rolls '71 and 72 are separated slightly as lever 86 retracts drive roll 71 against spring 87. Two belts of master duplicating material in the form of continuous loops are then slipped over drive rolls 71 and 72 with their respective support rolls '77 and 78. That is,belt 83 is slipped over drive roll 71 and support roll 77. A second belt 85 is slipped over drive roll 72 and support roll 78. Since there is no need of applying a tension to the belts, support rolls 77 and 78 are suitably positioned just far enough from drive rolls 71 and 72 to prevent excessive slack and slop in the belts. A stack of copy paper treated on both sides with a solution of the appropriate Chemical B is placed in receiving tray 80 and a two sided original, having a volatile colored reagent in the marking material, is positioned on top of the copy papers. drive rolls 71 and 72 and feed dog 81 so that the original document is fed first between two belts 83 and 85. Heat applied through the belts from the heated drive rolls 71 and 72 evaporates the volatile color reagent from the two sides of the original to condense on the adjacent surfaces of the belts. The original passes into the receiving tray 82 and the copy sheets are then fed by feed dog 81 between the two belts which now carry the volatile color reagent in the configuration of the markings on the original, Heat from drive rolls 71 and 72 evaporates portions of the color reagent from master belts 83 and 85 so that it reacts with the color reaction partner. Chemical B, on the adjacent surfaces of each of the copy sheets to form intensely colored duplications of the original document. After the desired number of copies have been run olf, belts 83 and 85 are removed from the apparatus and may be discarded or cleaned for reuse if desired. Both reusable and non-reusable belts can be supplied for use with the apparatus in FIG. 14. The non-reusable belts would be made of an inexpensive material such as paper, while the reusable belts would preferably be made of a good dimensionally stable base material such as polyethylene terphthalate with'a surface coating of polytetrafluorethyl- The invention method and apparatus has been described as producing copies printed on two sides from an original printed on two sides. However, it is equally easy to produce two copies printed on one side only from an original printed on both sides or one copy printed on both sides from two originals printed on one side. It is also possible to produce in one reproducing cycle two copies printed on one side from two originals printed on one side. These variations are only a matter of handling the originals and copy sheets in the right manner. Thus to make copies printed on one side from an original printed on both sides it is necessary to vary the previously described process only to the extent of using two sheets of copy paper simultaneously back-to-back instead of one sheet. To make one copy printed on both sides from two originals printed on one side, the two originals back-to-back are heated simultaneously between the master surfaces. In order to make copies printed on one side from originals printed on one side, two originals back-to-back are placed between the master surfaces and heated, then two copy sheets back-to-back and placed between the master surfaces and heated.

In accordance with the present invention, the number of reproduced copies is not strictly limited. However, a preferable quantity is 12 or less since a greater quantity Motor 76 is then actuated to operate of copies requires a large amount of Chemical A in the original and more accurate control over transfer than would otherwise be necessary. Many known economical machines exist to produce greater volume. It has been found, for example, that to make six copies, it is preferable to have for the average pica character about one microgram of a Chemical A such as rubeanic acid on the intermediate master sheet.

A given original in accordance with the invention is necessarily limited to producing one master. Although, as has been disclosed, a high percentage transfer of the voltatile chemical can be obtained, it is sometimes desirable to produce two masters. Thus, the originator and the recipient of a document might both desire to produce duplications in accordance with the invention. Faster transfers of lower heat will provide only a partial transfer of the volatile chemical for the first master. Enough of the volatile chemical is then retained in the original for making a further master.

While the illustrated embodiments of the invention have been described generally in relation to the reproduction of typewritten material, the invention is in no way limited to typewritten material. Handwritten material using a pen or machine drawn material using some form of stylus device, in which the pen or stylus uses a drawing solution containing color reagent Chemical A, is suitable as an original for reproduction in accordance with the inventive process. A usable original may also be produced by xerography from an original that does not contain a volatile color reagent. Such a xerographic copy for use as an original in the inventive process would be made using Chemical A in a developer material for the xerographic image. It has been found for example that rubeanic acid, itself, will act as a suitable toner in developing an electrostatic latent image in the xerographic process.

Also in the disclosed embodiments, the source of heat while generally described as a heated roller or cylinder is not limited to such but can be any source of heat capable of supplying the necessary heat to cause vaporization of Chemical A. Thus, photo-flash lamps, infrared lamps, any source of intense radiant illumination, sources for supplying hot air by blowers or convection currents and various electrical heating means are all contemplated as usable with the present inventive process. Various available machines may also be used such as the thermal processing machines available under the trade name, Thermo-Fax, available from Minnesota Mining and Manufacturing Company of St. Paul, Minnesota, and the thermal processing machines available under the trade name Kalfax, available from the Kalver Corporation of New Orleans, La.

In interpreting the appended claims, it is to be understood that the two master members recited therein may not only be flat but may also be round or oval as described in connection with FIGURES 13 and 14 of the drawings, and further may constitute two portions of one integral member, such as the two master members described in connection with FIGURES 9 and 11 which are made up of one folded sheet of master material.

It is also to be understood in connection with the interpretation of the claims that although it is obviously preferable to employ a completely impermeable copy sheet of the type which will not allow penetration of the heat voltalizable color reaction partner from one side of the copy sheet to the other so as to prevent the formation of ghost images on the second side of the copy sheet, a certain amount of this ghost imaging is tolerable where copy cost is paramount, and inexpensive copy sheets must be employed. Accordingly, the phrases substantially impermeable, when used to modify the copy sheet, shall be understood to mean that under the particular operating conditions of heat, pressure, volatility of the color-form ing reagent speed of operation and the like that the copy sheet shall be of such a character as to prohibit the penetration of all but a small percentage of the heat volatilized ll color-forming reagent at most so as to prevent the formation of all but faint ghost images at most.

While the present invention has been described as carried out in specific embodiments thereof, there is no desire to be limited thereby, but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. A duplicating method for preparing and duplicating a two-sided document comprising:

(a) applying visible intelligence to each of the two sides of an original sheet using a colored material containing a heat volatizable color reactive chemical;

(b) positioning said sheet between the faces of two non-porous master members;

() applying heat to said sheet so that said color reactive chemical evaporates and transfers to each of the said faces;

(0?) removing said sheet from between said two master members;

(e) positioning a substantially impermeable copy sheet treated with a color reaction partner for said color reactive chemical between said faces of said two master members;

(f) applying heat to said two master members so that said color reactive chemical evaporates and transfers from said two master members to said copy sheet forming an intensely colored duplication of said intelligence.

2. A duplicating method for preparing and duplicating a two-sided document comprising:

(a) imprinting an original document on both sides with marking material containing a heat volatilizable color reagent;

(b) placing said original between the faces of two master members to form a first sandwich;

(c) applying heat to said first sandwich so that said color reagent evaporates from one side of said original and transfers to the adacent one of said two master faces and said color reagent evaporates from the other side of said original and transfers to the other of said two master faces;

(d) removing said original from between said two master members;

(e) placing a substantially impermeable copy sheet treated with a color reactive partner for said color reagent between said two master faces to form a second sandwich;

(f) applying heat to said second sandwich so that said color reagent evaporates and transfers from each of said two master faces to the adjacent copy sheet surface where it reacts with said reaction partner in the copy paper to form an intensely colored reproduction of said original;

(g) removing said copy sheet from said sandwich; and

(h) repeating the steps of placing a copy sheet between said two master faces, applying heat, and removing the copy sheet a plurality of times using a fresh copy sheet each time so as to form a plurality of reproductions of said original.

3. A duplicating method according to claim 2 in which said placing said original, said removing said original and said placing copy paper comprises moving said two master faces synchronously together and successively passing said original and then said copy paper etwcen said two master faces.

4. A duplicating method according to claim 2 in which said applying heat to said first sandwich comprises heating said original to a temperature of 200 to 400 F. and said applying heat to said second sandwich comprises heating said two master faces to a temperature of 200 to 400 F.

5. A method of duplicating to produce copies carrying information on two sides comprising:

(a) forming two duplicating masters with volatile color reagent marking material in the mirror image configuration of information to be duplicated;

(b) positioning a substantially impermeable copy sheet treated on both sides with a color reaction partner for said marking material in between the information carrying surfaces of said masters;

(c) applying heat to the sandwich made up of said masters and said copy sheet to evaporate said volatile color reagent from said masters; and

(at) removing said heat so that said volatile color reagent condenses on said copy sheet forming \an intensely colored direct image of the information on the adjacent master surface on each side of said copy sheet.

6. A method of preparing and duplicating a two-sided document comprising:

(a) applying visible intelligence to each of two sides of Ian original sheet with a colored marking material containing a transferable component;

(b) positioning said original sheet between the faces of two master members;

(c) transferring at least a portion of said marking material on each side of said original sheet to the face of the master member facing it;

(d) removing said original sheet from between said two master members;

(e) positioning a copy sheet between said two master members with their marking material bearing faces towards said copy sheet; and,

(f) re-transferring at least a portion of said transferable marking material from the face of each of said master members to one of the opposite sides of said copy sheet and then separating said copy sheet from said master member whereby a two-sided duplicate of said original sheet is obtained.

; 7. A duplicating method comprising:

(a) positioning between the faces of two master members an original sheet bearing images on each of its two sides, said images made with a colored marking material containing a transferable component;

(b) transferring at least a portion of said marking material from the image on each side of said original sheet to the face of the master member facing it;

(c) removing said original sheet from between said two master members;

(d) positioning a copy sheet between said two master members with their marking material bearing faces toward said copy sheet; and,

(e) re-transferring at least ta portion of said transferable marking material from the face of each of said master members to one of the opposite sides of said copy sheet and separating said copy sheet from said master member whereby a two-sided duplicate of said original sheet is obtained.

8. A method according to claim 7 further including repeating the steps of placing a copy sheet between said two master member faces, transferring a portion of the remaining transferable component of the marking material from the face of each of said master members to one of the opposite sides of said copy sheet, and removing said copy sheet from between said masters using a fresh copy sheet each time so as to form a plurality of two-sided duplicates.

References Cited in the file of this patent UNITED STATES PATENTS 2,501,495 Carroll et al. Mar. 21, 1950 2,770,534 Marx Nov. 13, 1956 2,936,707 Maquire et al. May 17, 1960 3,121,650 Meissner Feb. 18, 1964 FOREIGN PATENTS 498,636 Great Britain Jan. 11, 1939 

1. A DUPLICATING METHOD FOR PREPARING AND DUPLICATING A TWO-SIDED DOCUMENT COMPRISING: (A) APPLYING VISIBLE INTELLIGENCE TO EACH OF THE TWO SIDES OF AN ORGINAL SHEET USING A COLORED MATERIAL CONTAINING A HEAT VOLATIZABLE COLOR REACTIVE CHEMICAL; (B) POSITIONING SAID SHEET BETWEEN THE FACES OF TWO NON-POROUS MASTER MEMBERS; (C) APPLYING HEAT TO SAID SHEET SO THAT SAID COLOR REACTIVE CHEMICAL EVAPORATES AND TRANSFERS TO EACH OF THE SAID FACES; (D) REMOVING SAID SHEET FROM BETWEEN SAID TWO MASTER MEMBERS; (E) POSITIONING A SUBSTANTIALLY IMPERMEABLE COPY SHEET TREATED WITH A COLOR REACTION PARTNER FOR SAID COLOR REACTIVE CHEMICAL BETWEEN SAID FACES OF SAID TWO MASTER MEMBERS; (F) APPLYING HEAT TO SAID TWO MASTER MEMBERS SO THAT SAID COLOR REACTIVE CHEMICAL EVAPORATES AND TRANSFERS FROM SAID TWO MASTER MEMBERS TO SAID COPY SHEET FORMING AN INENSELY COLORED DUPLICATION OF SAID INTELLIGENCE.
 7. A DUPLICATING METHOD COMPRISING: (A) POSITIONING BETWEEN THE FACES OF TWO MASTER MEMBERS AN ORIGINAL SHEET BEARING IMAGES ON EACH OF ITS TWO SIDES, SAID IMAGES MADE WITH A COLORED MARKING MATERIAL CONTAINING A TRANSFERABLE COMPONENT; (B) TRANSFERRING AT LEAST A PORTION OF SAID MARKING MATERIAL FROM THE IMAGE ON EACH SIDE OF SAID ORIGINAL SHEET TO THE FACE OF THE MASTER MEMBER FACING IT; (C) REMOVING SAID ORIGINAL SHEET FROM BETWEEN SAID TWO MASTER MEMBERS; (D) POSITIONING A COPY SHEET BETWEEN SAID TWO MASTER MEMBERS WITH THEIR MARKING MATERIAL BEARING FACES TOWARD SAID COPY SHEET; AND, (E) RE-TRANSFERRING AT LEAST A PORTION OF SAID TRANSFERABLE MARKING MATERIAL FROMTHE FACE OF EACH OF SAID MASTER MEMBERS TO ONE OF THE OPPOSITE SIDES OF SAID COPY SHEET AND SEPARATING SAID COPY SHEET FROM SAID MASTER MEMBER WHEREBY A TWO-SIDED DUPLICATE OF SAID ORIGINAL SHEET IS OBTAINED. 